Knee Straightening, Hip Turn
Posted October 11th, 2010 @ 05:49pm by Erik J. Barzeski
This video isn't meant to demonstrate anything except the very simple idea that the right (or rear) knee straightening allows your hips to turn. If you "maintain the knee flex" your hips can't turn properly.
This is related to this post on Phil Mickelson's swing as analyzed by Peter Kostis.